People are very bad witnesses. They have memory gaps from small to large, confuse things and sometimes lie consciously. So whoever relies on asking a person who has tested positive for Sars-CoV-2 about who they have met in the past 14 days, and that as a basis for finding contact persons – well. He will probably miss a lot of contacts.

Cell phone tracking is obvious. Goes fast, is digital, that is to say progressive, and other countries from Israel to China do that too. And other countries – like Israel and China – don’t care about the privacy of the population. Corona tracking and data protection do not have to be a contradiction.

Based on an app for Singapore, three authors, including the Berlin judge Ulf Buermeyer on netzpolitik.org, explained this. There are a few important thoughts in there, including: Using the radio cells, i.e. the cell phone data, for tracking is nonsense. Because they are far too rough. This would result in all people on the same subway being quarantined as contact persons – most of them unnecessarily.

The cell phone data also does not provide interior tracking: if, for example, an infected person was on the first floor, everyone who was on floors 2 to 15 would also be contact persons. That is why the authors propose acquisition via Bluetooth.

Smart, because it comes into play when people – that is, their cell phones – get close. So real contacts could be determined. And that, thanks to a constantly changing ID and a few other tricks, is also very privacy-friendly.

Of course, a few more points are important: Such an app must be voluntary. It should be open source so that it can be checked that it actually only does what it is supposed to do. There must be an installation route past the Google Play store and Apple’s iTunes, for example on the website of the Robert Koch Institute.

Protection against trolls necessary

A solution is needed so that people can enter their test results truthfully – and not trolls flood the system with false positive messages. And tracking, as unreliable as it is, must not replace human witnesses, after all, there are enough people without smartphones. And at least as important is to significantly increase the test capacities. Because if everyone who gets an app alarm is in quarantine without a test, the use becomes pretty unattractive.

Such an app will only be successful if people consider it trustworthy. Data protection is a prerequisite for this.